Earlier this year, a report by researchers at the University of Wisconsin – Green Bay identified the source of a naturally occurring chemical element in the deep-water aquifer of northeastern Wisconsin that could pose problems for children.
The element is called strontium, a naturally occurring element that along with arsenic and nickel were mixed in with sulfite minerals an estimated 350 million years ago when a hot brine washed through the area, said Dr. John Luczaj, Geoscience Chair of the Department of Natural & Applied Sciences at the University of Wisconsin – Green Bay.
“Now the water is dissolving these minerals, and what’s in the rocks controls the chemistry of the groundwater, like it does everywhere,” Luczaj said. “It’s not totally surprising. We knew there was a strontium problem in our area because in the 1950s people had done research that showed there were municipal wells with elevated strontium in eastern Wisconsin.”
What was not known was how that strontium came to be in such large amounts in the bedrock of the region, in what is known as the Cambrian-Ordovician aquifer system.
The research project came about when one of Luczaj’s students, Joseph Baeten, was looking for a graduate thesis project.
“I talked with a bunch of people, and they said nobody’s ever researched this and tried to figure out the source of this material and the geological story behind it,” Luczaj said. “It just happens to have a public health significance to it. Although it’s not one of the must crucial concerns people have with water quality, it is a concern.”
That concern is for children because strontium mimics calcium. When strontium is ingested by children, it can cause tooth mottling, rickets and bone deformities because the strontium is mimicking the calcium phosphate in bones and tooth enamel without the substance required for bone and tooth development. “Since it’s a different-sized atom (from calcium), it’s actually going to disrupt the structure a little bit, so you can get tooth enamel mottling and things like that,” Luczaj said.
However, strontium – or the specific compound strontium ranelate – is actually used to increase bone density in older adults.
The majority of the research was done in Brown and Outagamie counties, but also extended into Door County, and more than 60 percent of the samples collected had dissolved strontium values above the lifetime health advisory limit.
“A region of high dissolved [strontium] occurs in an arc-shaped band throughout eastern Wisconsin from suburban Milwaukee up through Brown, Outagamie, Calumet, Door, Oconto and Marinette counties,” the researchers stated in a report prepared for the University of Wisconsin Water Resources Institute.
The researchers – which included Luczaj, Baeten and Michael Zorn, also of the Department of Natural & Applied Sciences at UWGB – determined the source of the strontium to be from the dissolution of celestine in fissures and fractures in carbonate rocks.
“We wanted to figure out where the hot spots are in Brown and Outagamie counties, and then look further north to Door and other areas, and really find out what’s going on,” Luczaj said. “We were able to delineate the zones of high strontium. We looked at strontium isotopes and other things to try to fingerprint the source of the strontium by getting the isotopic components of the strontium in different minerals and then seeing which matched. The strontium sulfite mineral matched exactly with what we found in the water.
“The surprising thing was that we found the problem continued a little bit further to the north and east,” he continued. “In southwestern Door County, this problem does exist. A lot of people there know that there is stinky water or salty water. Everybody in the northern part, especially on the eastern side, their wells are quite different. They’re getting their water out of the dolomite. But people in the southwest along the bay are likely to have deeper wells. They don’t have bacteria nitrate problems, but they have some other issues with dissolved salts and things like this.”
Luczaj added that if you are in the area with high concentrations of strontium, it doesn’t matter if you have well water or municipal water, the strontium is coming through.
But there is a simple fix.
“A lot of people who have deeper wells have reverse osmosis systems,” he said. “Water softeners take this stuff out completely because it behaves like calcium.”